Nice little prototype! A cool concept and a nice implementation, I like that the danger level really decreases when you go out of sight of the enemy. It would be cool to have more complex levels, but for the very first game it is a very very solid submission! Keep going!
Also a little advice: to get more feedback and more people to play your game, upload a web version of your games as well, as far as I know gamemaker can make web builds. A lot of people just don't bother downloading executables and play only web based games. You can practice exporting your game and uploading it to itch as a web game to a separate test project, it shouldn't be that hard.